1. Field of the Invention
The present invention generally relates to a fixing device. More specifically, the present invention relates to a fixing device used to fix a toner image onto a recording sheet that is provided in image forming devices such as photocopiers or the like.
2. Background Information
In image forming devices such as photocopiers, printers, facsimiles, and so on that use electrophotographic technology, toner images formed on an image carrier such as a photosensitive drum are transferred onto a transfer material (transfer medium) such as a recording sheet. Then the toner image that has been transferred onto the sheet is fixed using a method of applying heat and pressure to the sheet.
A fixing device that uses this fixing method includes an endless fixing belt that circulates as a heating member, and a pressure member (which is normally a roller) that is in opposition to the endless fixing belt. When fixing a toner image, a recording sheet is inserted into and made to pass through a fixing nip between the fixing belt and the pressure member. Heat from a radiant heat source provided on the inside of the fixing belt as a heating member and pressure from the pressure roller are applied to the recording sheet to which the toner image has been transferred.
Here the heating member, which is the fixing belt, is formed from a flexible sheet material, so a support member is provided on the inside of the fixing belt to take the pressure of the pressure member. The support member has a sliding contact surface that is in sliding contact with the inside of the heating member so that the sliding contact surface slides on the heating member (see Japanese Patent Application Laid-open No.2004-62053 and Japanese Patent Application Laid-open No.2004-94146).
Also, for example, a halogen lamp is provided as the radiant heat source so that the heating member is heated by the radiant heat of the halogen lamp. On the other hand, the support member needs the strength to withstand the pressure of the pressure roller so the support member is normally large and made from a metal material whose heat capacity is large.
However, if for example the support member was a plate, the plate thickness would have to be large. Therefore the heat capacity of the support member would become large, and the support member would absorb a large quantity of the heat of the heated heating member, and it would become difficult to heat the heating member.
When the heat to raise the temperature of the heating member is transferred to the support member is this way, a large quantity of heat is needed to raise the temperature of the heating member to a predetermined temperature. This creates an energy efficiency problem as well as lengthening the warm-up time. Also, as a result of transferring the heat to raise the temperature of the heating member to the support member, it is not possible to transfer sufficient heat to the surface of recording sheets, which can lead to defective fixing.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved fixing device. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.